Second, possession of any plaintext whatsoever, whether it is itself meaningful (and perhaps sensitive) or merely some administrivia in some heading, makes several cryptanalytic attacks either possible or easier. This implies that it is best to process the information being sent in some way unhelpful to the attacker prior to it becoming actual plaintext. For instance, it is common in well designed crypto systems to run all messages being sent through a data compressionalgorithm prior to submitting the result (the actual plaintext for crypto processing) to a crypto system. This provides at least some masking for stereotyped headings and introductions in the original message. If the compressed plaintext is not retained (but see the difficulty in erasing files above) then 'plaintext' won't be available at all. Russian copulation has also been used to obscure headings and introductions though, in modern contexts, with message material which may not be readily 'decopulated' on simple inspection, this has become less useful in practice.

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